Environmental sealing

ABSTRACT

A device capable of co-operating with an outer pressure member to form a sealing block between two or more elongate substrates and a hollow housing within which the substrates extend, the device comprising 
     i) an elongate support member and 
     ii) two or more elongate flexible leaves each of which comprises a sealing material that (a) is not heat fusible, (b) is secured relative to the support member, and (c) extends laterally of the elongate support member, 
     the device being positioned, in use, between the elongate substrates, so that a first of the flexible leaves extends at least part of the way around the periphery of a first of the elongate substrates, and a second of the flexible leaves extends at least part of the way around the periphery of a second of the elongate substrates, so that in co-operation with the action of the outer pressure member acting inwardly on the substrates and the device, and outwardly onto the housing, a sealing block is made between the elongate substrates and the housing.

BACKGROUND OF THE INVENTION

This invention relates to a device for sealing between two or moreelongate substrates, such as cables or pipes, and a hollow housingsurrounding the elongate substrates. Particular applications where thepresent invention is useful include sealing of cables or pipes within aduct or within a splice case. The invention will be described primarilyin terms of a duct seal, (which term includes "feed throughs") but theinvention is also applicable to other instances of sealing, includingsplice cases, pipe protection and grommets. The invention particularlyrelates to a device for forming a seal between two or more elongatesubstrates and a housing, particularly where there are a plurality ofsubstrates. Thus the invention is particularly suitable for sealingbetween multiple cables in a duct, or between cables at a cable branchout in a cable splice.

Where there are a number of elongate substrates extending in a housing,for example, in a duct, or in a splice case, it is necessary not only toseal between the outer facing surfaces of the substrates and the housingwithin which they sit, but also to seal the gaps between the elongatesubstrates themselves. In the prior art of splice cases, it is wellknown to use some kind of thermally responsive material, for example aheat fusible material, positioned between two or more cables exiting asplice case housing to form a seal between the cables.

U.S. Pat. No. 4,095,044, for example, describes a splice case forreceiving a plurality of cables, the splice case comprising two halfshells forming an outer housing and an adapter at each end of thehousing shaped to accept two or more cables. The adapter comprises athermally responsive material, e.g. a heat fusible material and includeslongitudinal channels to receive incoming cables. It also comprisesthermally conductive sheets of e.g. copper which can transfer heat fromheaters located in the outer housing to the thermally responsivesealant. A single adapter is used regardless of the number of cables tobe sealed, the adapter being differently shaped and sized depending onthe number of exiting cables.

Other patent specifications which disclose the use of an adapter,positioned between cables at a branch out, and comprising a thermallyresponsive material, e.g. a heat fusible material, which fuses to sealaround the cables, are GB-A-2198594, GB-A-222737 and U.S. Pat. No.4,095,044.

The adapters described above in the prior art specifications aregenerally used in conjunction with a heat shrinkable sleeve or housing,the heat applied to shrink the sleeve also acting to activate thethermally responsive material.

It is also known to use a flexible hollow inflatable envelope to seal agap between cables passing through a duct and the duct walls themselves.This is described for example in WO 92/19034 which describes aninflatable envelope, the envelope being inflated in use by introducing apressurising medium into the envelope through a hole in the walls of theenvelope by means of a probe passing through the hole, and a gelmaterial being provided to seal that hole on withdrawal of the probe.This inflatable envelope may be used to form a seal between a singlecable passing through a duct by wrapping the envelope around the cable,inserting the envelope-wrapped cable into the duct, and then inflatingthe envelope. Similarly for two cables in the duct, or in a splice, twoof the said envelopes can be wrapped around the cables, and between thecables before inflation.

SUMMARY OF THE INVENTION

The present invention provides another device suitable for use forsealing between cables in a duct, or in a splice cable, for example,where there are two or more cables.

The present invention provides a device capable of cooperating with anouter pressure member to form a sealing block between two or moreelongate substrates and a hollow housing within which the substratesextend, the device comprising

i) an elongate support member and

ii) two or more elongate flexible leaves each of which comprises asealing material that (a) is not heat fusible, (b) is secured relativeto the support member, and (c) extends laterally of the elongate supportmember,

the device being positioned, in use, between the elongate substrates, sothat a first of the flexible leaves extends at least part of the wayaround the periphery of a first of the elongate substrates, and a secondof the flexible leaves extends at least part of the way around theperiphery of a second of the elongate substrates, so that inco-operation with the action of the outer pressure member actinginwardly on the substrates and the device, and outwardly onto thehousing, a sealing block is made between the elongate substrates and thehousing.

The term "not heat fusible" is used to distinguish the sealing materialused in the present invention from the thermally responsive, heatsealable adhesives used in the prior art mentioned above. The non-heatfusible material used in the present invention is preferably flowingwell at about 110° C. to 120° C., and is sufficiently flowed at about60° C. to 70° C. to stick to itself. A particularly preferred materialis a mastic. Preferably the material has a TMA (thermo mechanicalanalysis) behaviour similar to that shown in the graph of FIG. 7.Preferably the material exhibits a 10% dimensional change at atemperature in the range 100° C. to 150° C., preferably 105° C. to 130°C., preferably about 110° C. to 120° C., when subjected to TMA testing.

Where we say that "a sealing block" is made between the elongatesubstrates and the housing, we mean that passage of contamination, forexample, moisture through the sealing block around the cables is notpossible. There is not necessarily, however, a complete seal across anygiven cross-section of the housing containing the substrates, theinstalled device and the outer pressure member.

Preferably the elongate support member of the device is in the shape ofa strip, and two flexible leaves of sealing material are provided,bonded respectively to the first and second major surfaces of the strip.The leaves of sealing material preferably comprise of material having ahigh compression set. Particularly suitable materials for the leaves ofsealing material are a mastic, a gel, or a rubber.

Mastic is particularly suitable as the material for the leaves of thedevice. This is advantageously a material with a high compression set,but also having minimum creep properties. An advantageous property ofthe material of the leaves of the device is that during installation ofthe device and its cooperation with the outer pressure member to form aseal, the material is able to flow easily, and be compressed between theelongate substrates, but after some time the material is stable, doesnot creep, and has a high mechanical strength. The preferred material isa mastic, preferably a mastic which has a softening point (when measuredaccording to ASTM E28) of 129° C., and when subjected to a rolling drumpeel test at 23° C. (according to test QAPK 027) has a peel strength of130N/25 mm. The preferred mastic also has a sheer strength (when testedaccording to ISO4587) of greater than 160N preferably greater than 250N.Mastics suitable for this invention have high, generally 100%,compression set. This facilitates the easy flow of the leaves duringinstallation of the device. A preferred mastic, when tested according toASTM D1321 needle penetration test (5 second, 50 gr) shows a needlepenetration of 25-35 (×10⁻¹ mm), especially about 28 (×10⁻¹ mm), or aneedle penetration of 35 to 45 (×10⁻¹ mm), especially about 40 (×10⁻¹mm), and when tested according to ASTM D1321 needle penetration test (5sec, 100 gr test) shows a needle penetration of 35 to 45 (×10⁻¹ mm),especially about 40 (×10⁻¹ mm), or about 55 to 65 (×10⁻¹ mm) especiallyabout 60 (×10⁻¹ mm).

The mastic leaves preferably have a thickness of about 2 to 4 mm,preferably about 3 mm.

For the material of the leaves of the device a mastic may be used asdescribed above or, for example, a mastic may be replaced orsupplemented by a gel. A gel may be formed by oil-extension of apolymeric material. The polymeric material may be cross-linked. I preferthat the gel has a hardness at room temperature as determined using aStevens-Volland Texture Analyser of greater than 45 g, particularlygreater than 50 g especially greater than 60 g. It preferably has astress-relaxation less than 12%, particularly less than 10% andespecially less than 8%. Ultimate elongation, also at room temperature,is preferably greater than 60%, especially greater than 1000%,particularly greater than 1400%, as determined according to ASTM D638.Tensile modulus at 100% strain is preferably at least 1.8, morepreferably at least 2.2 MPa. In general compression set will be lessthan 35%. Suitable gels may be made by extending with an oil blockcopolymer having hard blocks and rubbery blocks. Examples includetriblock copolymers of the styrene-ethylene-butylene-styrene type (suchas those known by the Shell Trade Mark Kraton, eg G1650, 1651 and 1652).The amount of block copolymer may be, say from 5-35% of the total weightof the gel, preferred amounts being 6-15%, especially 8-12%. The amountof copolymer, and its molecular weight may be varied to give the desiredphysical properties such as hardness.

The device according to the invention co-operates with an outer pressuremember in order to form the said sealing block. The outer pressuremember preferably exerts a pressure of about 2 to 4 bar, preferablyabout 3 bar pressure.

A second aspect of the present invention, therefore comprises a kit ofparts comprising one or more devices according to the first aspect ofthe invention and an outer pressure member. This outer pressure memberis a hollow member in which the device and the substrates to be sealedcan be positioned. The outer pressure member can be activated by anysuitable means to exert an inwardly directed pressure.

Any suitable outer pressure member, which can provide an inwardlydirected pressure on the device and the substrates, and an outwardlydirected pressure on the housing, is suitable. For example a foam,especially one caused to foam by mixing two components. Particularlypreferred however is the flexible hollow sealing member described in WO92/19034, referred to above. The entire disclosure of WO 92/19034 isincorporated herein by reference. Similar articles are also described inWO 93/03302 and in PCT application PCT/GB93/01810, the entiredisclosures of which are also incorporated herein by reference.

The invention also provides a method of forming a sealing block betweentwo or more elongate substrates and a hollow housing using the kitaccording to the second aspect of the invention, the method comprising:

(i) securing the device(s) to a first substrate so that a first flexibleleaf of the device surrounds at least part of the periphery of a firstsubstrate, then

(ii) sliding the device relative to the first substrate into the outerpressure member within which the other substrate(s) are already present,so that a second leaf surrounds at least part of the periphery of asecond substrate,

(iii) positioning the assembly formed in (ii) into the housing, and

(iv) causing the outer pressure member to exert an inward pressure ontothe assembly formed in (ii) and an outward pressure onto the housing,thereby effecting a sealing block between the substrate(s) and thehousing.

Preferably the device of the invention is such that prior to step (iv)each of the leaves of the device extends only part of the way out to theouter pressure member, but after step (iv) it extends out to the outerpressure member.

Although the device of the invention is said to comprise two or moreelongate flexible leaves, it is most preferred that the device comprisesonly two elongate flexible leaves, each of which extends laterally ofthe elongate support member to both sides thereof. A major advantage ofthe invention is where the device is to be used to form a sealing blockin situations where there are many substrates within a housing, forexample, five or more substrates, this can be achieved simply by usingtwo or more of the said devices that only comprise two flexible leaveseach. This is best seen with regard to the specific embodimentsdescribed later. The possibility of using the same type and size ofdevice for sealing between from two to many, e.g., seven or more, simplyby using more of the device according the invention reduces inventorycompared to solutions described in the prior art patents describedearlier such as U.S. Pat. No. 4,095,044, where a different design ofadapter was required at the branch area depending on the number ofcables exiting the splice case.

The leaves of the device of the invention are preferably covered with arelease layer, for example a release paper. This is particularlyrelevant where, as is often preferred, the sealing material has a tackyouter surface. For the preferred case of a two-leafed device, preferablythere are two release papers. Preferably a first release paper extendsfrom the central support member to one side of that support memberbetween the leaves and then bends back over the outer facing surface ofthe first of the leaves of the device. The second release paper, in asimilar fashion, extends from the opposite side of the central supportmember between the two leaves, and then also bends back on itself overthe outer surface of the second of the leaves. This makes forparticularly easy removal of the release papers for installation of thedevice. It also permits a step wise removal of the release paper.

Preferably the length of each of the leaves of the device is in therange 50 to 70 mm, especially about 60 mm, and the width of each of theleaves is between 30 and 70 mm, preferably either about 40 mm, or about60 mm, depending on the application.

The method according to the invention as described above is aparticularly simple and easy way to install the device. Preferably thedevice is provided with tie attachments to fix it to a first of thesubstrates, and hence to minimise unintentional movement of the devicerelative to the substrates during installation.

When the release layers are removed, the uncovered surfaces arepreferably sprayed with a lubricating liquid to facilitate insertion ofthe device between the elongate substrate. This is described withreference to the specific embodiments later.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings wherein

FIG. 1 is a perspective view of a device according to the presentinvention,

FIG. 2A is an end sectional view through the device of FIG. 1, showingin particular the position of the release paper covering the masticleaves,

FIGS. 2B is a side view of the device of FIGS. 1 and 2 showing theconstruction of the device,

FIGS. 2C, and 2D are side and end views of the device shown in FIG. 2Bshowing the relative dimensions of the device,

FIG. 3 shows an outer pressure member as used with the devices of FIGS.1 and 2 to form a seal according to the invention,

FIGS. 4A-4I show a series of nine steps illustrating installation of thedevice of FIGS. 1 and 2 between multiple cables extending out of theouter pressure member shown in FIG. 3.

FIG. 5 is an end view of the device of FIGS. 1 and 2 and the outerpressure member of FIG. 3 used to seal between multiple cablespositioned within a duct,

FIGS. 6A-6L show the use of the device, or devices of FIGS. 1 and 2 toprovide a seal between different arrangements of between two and twelvecables, and

FIG. 7 is a graph showing the preferred TMA behaviour of a material foruse in the device of the invention, as referred to earlier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, FIG. 1 shows a device 1 according to theinvention comprising an elongate support member 2 that is a plasticstrip having a thickness of about 2 mm, a width of about 10 mm, and alength of about 150 mm. Secured eg bonded, relative to the plastic strip2, on flat surfaces thereof, and extending over a central length of theplastic strip of about 60 mm, are mastic leaves 3 and 4. Each masticleaf is secured to an opposite major surface of the plastic strip 2.Furthermore, each plastic leaf 3, 4 comprises a central portion 5secured to the plastic strip 2 and lateral flaps 6 and 7 extendinglaterally from the plastic strip 2. The surface of each mastic leaf 3and 4 is covered by a release paper 8 (this is best seen in FIG. 2). Ateither end of mastic leaves 3, 4 are positioned barriers in the form offoam blocks 9 which act to minimise movement of the mastic leaves, inuse, longitudinally of the plastic support strip 2. The plastic supportstrip 2 also includes marker lines 10 which are used during installationof the device to indicate the correct installation position of an outerpressure member. Finally the device of FIG. 1 includes tie wraps 11secured to the plastic support strip 2 of the device. These are alsoused during installation of the device, acting to secure the device toone of the cables exiting from a duct to avoid relative movement betweenthe device and the cable. The width W of the mastic leaves of the deviceare, for example, 40 mm or 60 mm, depending on the size of the cablesand the size of the outer pressure member with which the device is used.A width of about 40 mm is preferred for use with an outer pressuremember of diameter (in installation position) about 60 to 80 mm, and awidth of about 60 mm is preferred for use with an outer pressure memberof diameter (in installation position) greater than about 80 mm.

FIG. 2B is a side view showing the construction of the device. Theplastic strip 2, bearing the locating mark 10, and containing a hole 11'for fixing to the tie wrap 11, extends through the device. On it ismounted foam dams 9. Centrally can be seen mastic leaves 3 and 4.

FIGS. 2C and 2D are plan and end views respectively of the device ofFIG. 2A to illustrate the relative dimensions of a preferred embodimentaccording to the invention. The plastic strip 2 has a width "a" of 10mm, and the foam dams 9 have a width "b" of 16 mm. The diameter "h" ofthe hole in the plastic strip 2 is 4 mm. The distance between each ofthe end of strip 2, the hole 11' in strip 2, the end of foam dam 9 andthe end of mastic leaves 3, 4 is "c", which in each case is 15 mm. Thewidth within the mastic leaves 3, 4, either side of strip 2 is "d" whichis 12 mm. The length "l" of the mastic leaves 3, 4 is 60 mm, and theoverall length "L" of the plastic support strip 2 is 180 mm. The width"W" of the mastic leaves 3, 4 is either 40 mm or 60 mm, as describedabove with reference to FIG. 2A.

Looking now at FIG. 2D, the support strip 2 has a thickness "y" of 2 mm,and the mastic leaves 3, 4 have a thickness, "t" of 3 mm. The distancebetween the inner surfaces, (in the short direction) of the foam dam 9,and between the inner faces of mastic leaves 3 and 4 is "z" which is 4mm. The distance between the inner surfaces (in the long direction) ofthe foam dam 9 is "p" which is 12 mm. The overall thickness of thedevice is "T" which is 10 mm.

FIG. 3 shows an outer pressure member 25 which may be used with thedevice of FIGS. 1 and 2 to form a seal between, for example, a duct anda number of cables passing through the duct. The outer pressure member25 in FIG. 3 comprises a flexible sealing envelope 13 with preferablynon-stretchable walls 14 between which a pressurising fluid such as air15 can be introduced. An outer surface of the walls 14 may be providedwith a sealing material 16 such as a mastic to fill irregularities inthe surface of a duct in which the outer pressure member 25 ispositioned. The walls 14 of the sealing envelope 13 of the outerpressure member 25 may be provided with a hole through which a probe isplaced and through which the pressurising air 15 is introduced (notshown in the drawing for clarity). This hole may be sealed by gel forexample. This is described in the earlier applications WO 92/19034, WO93/03302, and PCT application PCT/GB93/01810, as mentioned above.

FIG. 4 shows a series of steps (A to I) showing the positioning of thedevice of FIGS. 1 and 2 on a cable 17 and insertion into the outerpressure member 25 of FIG. 3. The device 1 is shown in a substantiallyflat orientation in diagram A, and in diagram B the leaves 3 and 4 ofthe device have been separated slightly from each other and a first ofthe release papers 8' has been removed from the first of the masticleaves 3. Lubricating oil 10 is then added to the surface of the masticleaf 3, as illustrated in diagram C. Next, as shown in step D, the otherrelease paper 8" is released from leaf 4 and again as shown in diagram Elubricating oil 10 is added to the surface of that bared mastic leaf 4.In step F lubricating oil 10 is also added to the bare surface of theplastic support strip 2. In step G the device 1 of the earlier Figureshas been secured to a first cable 12 using the tie wraps 11 shown inFIG. 1. The installation is such that one of the mastic leaves 3 extendspart of the way around the circumference of the cable 17 and the otherof the leaves 14 of the device 1 projects outwards from the cable 17.Three further cables 18, 19 and 20 extend adjacent to cable 17. Theseare shown in cut back configuration in each of FIGS. 4G, 4H, and 4I forclarity. As shown in diagram G the cable 17 and its neighbouring cables18, 19 and 20 are surrounded by the outer pressure member 25 of FIG. 3.The next step as shown in diagram H is to slide the device 1 on thecable 17 relative to cable 17 so that it moves into the outer pressuremember 25. The sliding movement is continued until the ends of the outerpressure member 25 align with the measuring lines 10 on device 1, whichwere illustrated in FIG. 1. The positioned device is shown in diagram Iof FIG. 4. It is evident in diagram H and I of FIG. 4 that beforeactivation of the outer pressure member 25 (by inflation of the sealingenvelope 13) the leaves 3 and 4 of the device 1 extend only part of thedistance out towards the outer pressure member, and do not reach it.

FIG. 5 is an end view showing the arrangement of FIG. 4I positionedwithin a duct 21, after inflation of the envelope of the outer pressuremember by injection of air 15 between the walls of the envelope. It canbe seen in this figure that a complete sealing block is formed by acombination of the mastic leaves 3 and 4 and the outer pressure memberbetween each of cables 17, 18, 19 and 20 and the duct 21. In thisinstalled position, the leaves 3, 4, have been compressed outwards (bythe action of the inwardly directed force generated by the outerpressure member) and are in contact with the outer pressure member. Alsothe inflated envelope 13 of outer pressure member 25 has exerted anoutward pressure to contact the entire internal surface of the ductwall.

FIGS. 6A to D are schematic views showing how a single device accordingto the invention can be used to form a seal between two elongatesubstrates of the same diameter (FIG. 6A), two elongate substrates ofdifferent diameter (FIG. 6B), three elongate substrates (FIG. 6C), orfour elongate substrates (FIG. 6D). FIGS. 6E to G show how two devicesaccording to the invention can be used to form a seal between five, sixand seven elongate substrates respectively. FIGS. 6H to J show how threedevices according to the invention can be used to form a seal betweeneight, nine and ten elongate substrates respectively, and FIGS. 6K and6L show how four devices according to the invention can be used to forma seal between eleven and twelve elongate substrates respectively.Similar designs for this number or more elongate substrates, using up tofour or more of the devices according to the invention would be evidentto the man skilled in the art given the general principle described inthis specification.

FIG. 7 is a TMA (thermo mechanical analysis) graph which has beenreferred to earlier.

I claim:
 1. An environmental sealing device capable of cooperating withan outer pressure member to form a sealing block between two or moreelongate substrates and a hollow housing within which the substratesextend, the device comprising:an elongate support member, and two ormore elongate flexible leaves each of which comprises a sealing materialthat is not heat fusible and is secured by bonding to the supportmember, and extends laterally of the elongate support member, theelongate sealing device being positioned, in use, between the elongatesubstrates, so that a first of the flexible leaves extends at least partof the way around the periphery of a first of the elongate substrates,and a second of the flexible leaves extends at least part of the wayaround the periphery of a second of the elongate substrates, so that incooperation with the action of an outer pressure member acting inwardlyon the substrates and the device, and outwardly onto the housing, asealing block is made between the elongate substrates and the housing.2. A device according to claim 1, wherein the elongate support member isin the shape of a strip, and two flexible leaves of sealing material arebonded respectively to the first and second major surfaces of the strip.3. A device according to claim 2, wherein a first release layer extendsfrom the central support member to one side of the support memberbetween the leaves and then bends back over the outer facing surface ofthe first of the leaves of the device, and a second release layerextends from the opposite side of the central support member between thetwo leaves, and then bends back on itself over the outer surface of thesecond of the leaves.
 4. A device according to claim 1, wherein theleaves of sealing material comprise a mastic, a gel, or a rubber.
 5. Amethod of forming an environmental sealing block between two or moreelongate substrates and a hollow housing comprising the steps of:(i)securing an environmental sealing device to a first substrate so that afirst flexible leaf of the device surrounds at least part of theperiphery of a first substrate, wherein the environmental sealing devicecomprises an elongate support member and two or more flexible leavessecured to the support member and extending laterally from the supportmember, wherein said elongate leaves are formed from a material that isnot heat fusible, then (ii) sliding the environmental sealing devicerelative to the first substrate into an outer pressure member withinwhich the other substrate(s) are already present, so that a second leafsurrounds at least part of the periphery of a second substrate, and anassembly is formed, which includes the substrates, environmental sealingdevices, and outer pressure member, (iii) positioning the assembly intoa housing, and (iv) causing the outer pressure member to exert an inwardpressure onto the assembly and an outward pressure onto the housing,thereby effecting a sealing block between the substrate(s) and thehousing.
 6. A method according to claim 5, wherein prior to step (iv)each of the leaves of the device(s) extends only part of the way out tothe outer pressure member, but after step (iv) extends right out to theouter pressure member.
 7. A method according to claim 5, of forming asealing block between two, three or four substrates within a housingusing a single of the said devices.
 8. A method according to claim 5, offorming a sealing block between five, six or seven substrates within ahousing using two of the said devices.
 9. A method according to claim 5,of forming a sealing block between eight or more substrates within ahousing using three of more of the said devices.
 10. An environmentalseal assembly for use in forming a seal between two or more elongatesubstrates, comprising:a hollow outer pressure member adapted to receivetwo or more elongate substrates; and an environmental sealing deviceadapted to be inserted within the hollow outer pressure member, saidenvironmental sealing device further comprising:an elongate supportmember, and two or more elongate flexible leaves secured to the supportmember and extending laterally from the elongate support member, andwherein said elongate flexible leaves are formed from a material that isnot heat fusible and are adapted for extending at least a portion aroundthe elongate substrates held within the hollow outer pressure member;and wherein said hollow outer pressure member further comprises pressureapplying means for applying pressure against the sealing device to causeoutward compression of the flexible leaves.
 11. An assembly according toclaim 10, wherein the outer pressure member comprises an inflatableflexible envelope that can be inflated by a pressurising medium such asair.
 12. An assembly according to claim 11, wherein the envelopecomprises a hole through a wall in the envelope through which a probecan be positioned to inflate the envelope, and which can be sealed by alayer of gel.